The present invention is directed to a ground engaging drive track apparatus for a snowmobile vehicle or the like.
Snowmobiles and other all-terrain vehicles may advantageously employ a drive means in the form of an endless track assembly or unit mounted within a tunnel in a supporting chassis. The track unit includes an endless rubber-like belt having outer ground engaging ribs or cleats to propel the vehicle. An internal suspension system is provided to maintain proper ground engagement of the cleats of the lower run of the endless belt. The suspension systems are generally of a bogey-wheel or a slide rail construction. Slide rail suspension systems are particularly advantageously employed in high speed drive systems for such vehicles such as racing vehicles and the like, in order to establish and maintain maximum lineal support and minimum undulation in the flexible endless drive track unit. An extremely satisfactory slide rail suspension system is particularly and fully disclosed in Applicant's copending application entitled "SUSPENSION APPARATUS FOR GROUND ENGAGING DRIVE TRACKS" filed Apr. 1, 1974 and bearing Ser. No. 456,478, wherein a pair of slide rails slidably engaging the upper surface of a belt track member along the length of the lower run. In order to maximize the effective ground track engagement, various belt systems have been developed which incorporate generally U-shaped "grouser" bars formed as a part of the belt. The bars extend laterally across the track with the lower depending edges located so as to form ground engaging cleat and drive elements. Generally the grouser bars are either molded or otherwise attached to the bottom portion of the snowmobile track with the edges projecting downwardly into the ground engagement. In at least one embodiment of prior art construction such bars are fully embedded into the rubber track base belt with the lower or outer portion or run exposed to engage the ground and the lower portion or run exposed only in the areas of the slide rail.
Although such systems provide improved drive, Applicant has found that the exposed edges of the metal bars are not as effective on ice and the like as a more conventional molded rubber cleat. Further, when running on a hard surface, the temperature of the metal bars increase significantly as a result of frictional contact with the slide rail. This reduces the efficiency of the drive means, as well as presenting a source of possible severe damage to the track assembly. Although special lubrication can be provided, the system would be more complicated and rely on the satisfactory and continued functioning of the system.
In summary, although the grouser bar type of snowmobile track has been satisfactorily employed, Applicant has noted the distinct disadvantages associated with the unit from a practical standpoint and particularly an optimum construction in operation of high speed snowmobile units and other all-terrain vehicles.